1. Field of the Invention
The invention relates to a device for recording a digital information signal in an information track on a magnetic record carrier, and for converting, prior to recording, n-bit information words in the presented digital information signal into (n+m)-bit channel words, where n and m are integers and for which holds m.gtoreq.1 and n&gt;m, comprising
an input terminal for receiving the n-bit information words, PA0 an encoding device having an input coupled to the input terminal and having an output, which encoding device comprises an aT precoder, a being an integer greater than or equal to two and T being the bit period of the information words, which encoding device is arranged for converting the n-bit information words into the (n+m)-bit channel words and for presenting the channel words at the output, PA0 a recording device having an input coupled to the output of the encoding device, for recording the (n+m)-bit channel words in the information track on the magnetic record carrier.
2. Description of the Related Art
A device of this type is known, for example, from European Patent Application No. 339,724. In such prior-art device an encoding is described according to which an n-bit information word by utilizing is converted into an (n+m)-bit channel word a look-up Table is, subsequent to which the channel word is applied by means of a 2T precoder to a recording device which records the thus encoded (n+m)-bit channel word is on a magnetic record carrier. In this context NRZ-I recording is denoted. More specifically, an 8-to-10 bit conversion is described in which for each 8-bit information word at least three 10-bit words from the aforementioned Table each having a mutually different disparity are available.
With an appropriate selection from these three 10-bit words the running digital sum value in the serial channel word data stream at the output of the precoder can be controlled in such a way that a desired variation of this running digital sum value is realised as a function of time.
In above publication a pilot signal is thus accommodated in the serial data stream, which pilot signal when reproduced from the record carrier may, for example, be used to control tracking.